I am having this issue with the Meraki labs too. Looks like its a re-occurrence of the issue linked below, which needed someone from Cisco to fix?
https://community.cisco.com/t5/devnet-sandbox/meraki-enterprise-and-small-business-labs-fail-at-reservation/td-p/4066317
Error i get is
Error: Script runner exited with exit code: 1
Description: Exiting on error: 400 {"errors":["Email has already been taken","Email zowu@cisco.com is already registered with a Cisco Meraki Dashboard account. For security purposes, that user must verify his/her email address before administrator permissions can be granted here."]}
